Longitudinal study of the development of osteoarthritis and musculoskeletal disability in 961 individuals aged 50-72 is currently in its seventh year. Initial cross-sectional and two-year longitudinal data have been reported, and five-year data are being analyzed at present. This project extends the study an additional five years, entering the study phase where initial hypotheses may be addressed more definitively. The proposed study consists of six sub-projects. First, continued execution of data acquisition protocols including close follow-up and high retention rates in the study over time and reliability and validity studies. These data will provide the substrate for the remaining sub- projects. Second, analysis of the rate of development of musculoskeletal disability and the variables which are the best predictors of accelerated musculoskeletal disability in a community population. Third, analysis of the rate and best predictors of development of radiologic osteoarthritis in a smaller intensively studied group. Fourth, a seven and ten year comparison of the development of musculoskeletal disability in runners and non-runners. Fifth, an eight-and eleven-year study of the development of radiologic osteoarthritis comparing runners and non- runners in an intensive study group. Sixth, studies of the rate of development of osteopenia and the factors which affect this rate.